rc4.cpp

rc4加密算法,VC++源代码

#include <stdio.h> 
#define buf_size 1024  
typedef struct rc4_key  
{  
  unsigned char state[256];   
  unsigned char x; 
  unsigned char y; 
} rc4_key;  
#define swap_byte(x,y) t = *(x); *(x) = *(y); *(y) = t  
void prepare_key(unsigned char *key_data_ptr, int key_data_len, rc4_key *key) 
{  
int i;  
unsigned char t;  
unsigned char swapByte; 
unsigned char index1; } 
unsigned char index2;
unsigned char* state; 
short counter;
 
state = &key->state[0];  
for(counter = 0; counter < 256; counter++)  
state[counter] = counter; 
key->x = 0;  
key->y = 0; 
index1 = 0; 
index2 = 0;  
for(counter = 0; counter < 256; counter++) 
{   
  index2 = (key_data_ptr[index1] + state[counter] + index2) % 256;
  swap_byte(&state[counter], &state[index2]);  
  index1 = (index1 + 1) % key_data_len;  
}   
}  
 
void rc4(unsigned char *buffer_ptr, int buffer_len, rc4_key *key) 
{   
unsigned char t;  
unsigned char x; 
unsigned char y;  
unsigned char* state; 
unsigned char xorIndex;
short counter; 
 
x = key->x;  
y = key->y; 
state = &key->state[0];
for(counter = 0; counter < buffer_len; counter++)
{  
  x = (x + 1) % 256;  
  y = (state[x] + y) % 256;  
  swap_byte(&state[x], &state[y]); 
  xorIndex = (state[x] + state[y]) % 256; 
  buffer_ptr[counter] ^= state[xorIndex];   
}   
key->x = x; W..q.y<:N.  
key->y = y; {7 .nB.%SE  
}  
 
int main(int argc, char* argv[])
{  
char seed[256];  
char data[512];  
char buf[buf_size];  
char digit[5];  
int hex, rd,i;  
int n;   
rc4_key key;  
  
if (argc < 2) 
{   
  fprintf(stderr,"%s key <in >out\n",argv[0]); 
  exit(1); 
}   
strcpy(data,argv[1]); 
n = strlen(data);  
if (n&1)  
{  
  strcat(data,"0");   
  n++;  
} 
n/=2; 
strcpy(digit,"AA");  
for (i=0;i<n;i++) 
{   
  digit[2] = data[i*2]; 
  digit[3] = data[i*2+1];  
  sscanf(digit,"%x",&hex);
  seed[i] = hex;  
}   
 
prepare_key(seed,n,&key); 
rd = fread(buf,1,buf_size,stdin); 
while (rd>0) 
{  
  rc4(buf,rd,&key); 
  fwrite(buf,1,rd,stdout); 
  rd = fread(buf,1,buf_size,stdin); 
}  
}